Molded semiconductor device with header leads

Abstract

Header leads in a molded semiconductor device according to this invention are composed of electrode portions for securing a semiconductor pellet, and lead portions for connection. Each of the electrode portions is constructed of two tabular header portions separated from each other, and a columnar neck portion coupling both the header portions between opposing surfaces thereof. The lead portion is joined to one of the tubular header portions so that the lead portion and the columnar neck portion may extend coaxially. The cross-sectional area of the columnar neck portion in a direction orthogonal to the direction of the axis is larger than the cross-sectional area of the lead portion in the orthogonal direction. The semiconductor pellet is secured to the other header portion of each electrode portion. A mold material covers the entire periphery of the device from the semiconductor pellet to the one header portion of the electrode portion.

We claim: 
     
       1. A molded semiconductor device with header leads, comprising: a. at least one semiconductor pellet having at least one p-n junction,   b. a pair of electrode leads holding said semiconductor pellet therebetween, each of said electrode leads comprising; 1. an electrode portion, and   2. a connecting lead portion which is formed of the same metal as that of said electrode portion,   3. said electrode portion including two tabular header portions separated from each other, and a columnar neck portion coupling both of said header portions between opposing surfaces thereof,   4. said lead portion and said neck portion extending coaxially,   5. said lead portion being joined to a first of said two header portions of said electrode portion,   6. said neck portion having a cross-sectional area in a direction orthogonal to the axial direction which is larger than that of said lead portion,   7. said semiconductor pellet being secured to the second of said two header portions of said electrode portion,     c. first means including solder material for securing said semiconductor pellet to said second header portion of each of said electrode portions, and   d. second means including mold material for encapsulating said semiconductor device from said first header portion of one of said electrode portions to said first header portion of the other electrode portion, so as to cover the entire periphery of said semiconductor pellet.   
     
     
       2. A molded semiconductor device with header leads according to claim 1, wherein said neck portion of said electrode portion of each of said electrode leads is provided with at least three protrusions axially extending from said first header portion to said second header portion. 
     
     
       3. A molded semiconductor device with header leads according to claim 1, wherein said neck portion of said electrode portion of each of said electrode leads has a polygonal cross-sectional configuration in said direction orthogonal to said axial direction. 
     
     
       4. A molded semiconductor device with header leads according to claim 1, wherein each of said electrode leads is integrally formed of a metal which has a coefficient of thermal expansion in the range of 11×10 -6  /° C. to 20×10 -6  /° C., and wherein said electrode leads having those portions in contact with said mold material is provided with a glass non-adherent film, said mold material being a glass. 
     
     
       5. A molded semiconductor device with header leads according to claim 4, wherein each of said electrode leads is formed of copper or a copper alloy, said semiconductor pellet is composed of silicon, and wherein stopper means for checking mutual diffusion between copper and silicon are respectively disposed between said second header portions of said electrode leads and said semiconductor pellet, said stopper means being secured to said second header portions of said electrode leads and said semiconductor pellet by said solder material. 
     
     
       6. A molded semiconductor device with header leads according to claim 5, wherein said stopper means are composed of a ferro-alloy, molybdenum or tungsten. 
     
     
       7. A molded semiconductor device with header leads according to claim 4, wherein said semiconductor pellet has a mesa geometry. 
     
     
       8. A molded semiconductor device with header leads according to claim 7, wherein said second header portion of said electrode portion has a diameter which is equal to that of a principal surface of said semiconductor pellet at a smaller area side of said semiconductor pellet, and which is larger than that of said neck portion. 
     
     
       9. A molded semiconductor device with header leads according to claim 1, wherein said mold material is a synthetic resin. 
     
     
       10. A molded semiconductor device with header leads, comprising: a. at least one semiconductor pellet having at least one p-n junction,   b. a pair of electrode leads holding said semiconductor pellet therebetween, each of said electrode leads comprising;   
     
     
       1. an electrode portion including two tabular header portions separated from each other, and a columnar neck portion coupling said two header portions between opposing surfaces thereof, and 2. a connecting lead portion extending coaxially with said columnar neck portion of said electrode portion, said lead portion being joined to a first of said header portions of said electrode portion,   3. said semiconductor pellet being secured to a second of said header portions of said electrode portion,   4. said first header portion, said neck portion of said electrode portion, and said connecting lead portion being integrally formed together of an identical metal, wherein a cross-sectional area of said neck portion in a direction orthogonal to the axial direction is larger than that of said lead portion,   c. first means including solder material for securing said semiconductor pellet to said second of said header portions of said electrode portions, and   d. second means including mold material for enclosing said device from said first header portion of one of said electrode portions to said first header portion of the other electrode portion, so as to cover the entire periphery of said semiconductor pellet.   
     
     
       11. A molded semiconductor device with header leads according to claim 10, wherein said neck portion of each of said electrode leads is provided with at least three protrusions extending from said first header portion to said second header portion. 
     
     
       12. A molded semiconductor device with header leads according to claim 10, wherein said neck portion of each of said electrode leads has a polygonal cross-sectional configuration in said direction orthogonal to said axial direction. 
     
     
       13. A molded semiconductor device with header leads according to claim 10, wherein: 1. said first header portion, said neck portion and said lead portion of each of said electrode leads are formed of copper or a copper alloy.   2. said semiconductor pellet is composed of silicon, and   3. said second header portion of each of said electrode leads is made of a metal which checks mutual diffusion between copper and silicon.   
     
     
       14. A molded semiconductor device with header leads according to claim 13, wherein said second header portion of each of said electrode leads is composed of a ferro-alloy, molybdenum or tungsten. 
     
     
       15. A molded semiconductor device with header leads according to claim 10, wherein: 1. said mold material is glass, and   2. said first header portion of each of said electrode leads and said neck portion having contact with said mold glass are provided with a glass non-adherent film.   
     
     
       16. A molded semiconductor device with header leads according to claim 10, wherein said semiconductor pellet has a mesa geometry. 
     
     
       17. A molded semiconductor device with header leads according to claim 10, wherein said second header portion of each of said electrode leads has a diameter which is equal to that of a principal surface of said semiconductor pellet at a smaller area side thereof, and which is larger than that of said neck portion. 
     
     
       18. A molded semiconductor device with header leads according to claim 10, wherein said mold material is a synthetic resin. 
     
     
       19. A method of manufacturing a mold semiconductor device with header leads comprising the steps of: a. arranging at least one semiconductor pellet having at least one p-n junction between a pair of electrode leads, said semiconductor pellet and said pair of electrode leads having a different coefficient of thermal expansion,   b. securing said semiconductor pellet to said electrode leads by using an intermediate material having a predetermined melting temperature, and   c. encapsulating said semiconductor pellet in a molding material at a temperature greater than said predetermined temperature, so that thermal stresses are substantially eliminated on said semiconductor pellet.   
     
     
       20. A molded semiconductor device with header leads, comprising: a. at least one semiconductor pellet,   b. a pair of electrode leads holding said semiconductor pellet therebetween, each of said electrode leads comprising: 1. an electrode portion including first and second tabular header portions separated from each other, and a neck portion coupling said two header portions between opposing surfaces thereof,   2. l a connecting lead portion extending coaxially with said neck portion of said electrode portion, said lead portion being joined to said first header portion of said electrode portion, and   3. said connecting lead portion, said first header portion, said neck portion, and said second header portion being sequentially formed in order and being formed integrally together of an identical metal, wherein said neck portion has a cross-sectional area in a direction orthogonal to the axial direction larger than that of said lead portion,     c. stopper means being disposed between said second header portions of said electrode leads and said semiconductor pellet for preventing mutual diffusion therebetween,   d. first means including solder material for securing said semiconductor pellet to said stopper means, and   e. second means including mold material for enclosing said device from said first header portion of one of said electrode portions to said first header portion of the other electrode portion, so as to cover the entire periphery of said semiconductor pellet.   
     
     
       21. A molded semiconductor device with header leads according to claim 20, wherein said neck portion of each of said electrode leads is provided with at least three protrusions extending from said first header portion to said second header portion. 
     
     
       22. A molded semiconductor device with header leads according to claim 20, wherein said neck portion of each of said electrode leads has a polygonal cross-sectional configuration in said direction orthogonal to said axial direction. 
     
     
       23. A molded semiconductor device with header leads, comprising: a. at least one semiconductor pellet having at least one p-n junction,   b. a pair of electrode leads holding said semiconductor pellet therebetween, each of said electrode leads including an electrode portion having two tabular header portions separated from each other, a neck portion coupling said two header portions between opposing surfaces thereof, and a connecting lead portion extending coaxially with said neck portion of said electrode portion, said lead portion being joined to a first of said header portions of said electrode portion, wherein said neck portion has a cross-sectional area in a direction orthogonal to the axial direction which is largar that than of said connecting lead portion,   c. first means for securing said semiconductor pellet to a second of said header portions of said electrode portions, and   d. second means including mold material for enclosing said device from said first header portion of one of said electrode portions to said first header portion of the other electrode portion, so as to cover the entire periphery of said semiconductor pellet.   
     
     
       24. A molded semiconductor device according to claim 23, wherein at least said connecting lead portion, said first of said header portions, and said neck portion are integrally formed together of the same material.